The mystery of the dragon-tree

The recent popularity of dragon-trees has meant the tree is a common sight in Auckland suburban gardens. Strangely, the trees planted in the last 20 years look very different to those planted in the city a century earlier.

Dense branches and red 'dragon's blood'

El Drago Milenario is reputedly the largest and oldest living dragon-tree. Located in the Canary Islands, it has descending aerial roots that reach down to the ground from the lower branches. 5 May 2011.

Auckland War Memorial Museum - Tāmaki Paenga Hira.

Dragon-trees (Dracaena draco) are in the same monocot family as cabbage trees (Cordyline species). They are native to the Canary, Madeira and Cape Verde Islands, and the Atlas Mountains in Morocco.

The trees have glaucous sword-like leaves that are bunched at the end of the branch, in a similar way to the cabbage tree. Young plants have a single fat trunk, after each flowering the branch divides into two. The result is a tree with multiple branches.

The flowers are produced in large clusters. Once pollinated, shiny olive-green fruit develops and ripens to an orange colour. Each fruit contains two fat, roundish seeds with a slight flattened face. A cluster of flowers produces several thousand fruit.

In its native habitat, dragon-trees are typically a tight umbrella shape, with dense branches.

The largest and oldest living dragon-tree is believed to be El Drago Milenario, in the Canary Islands. It is estimated to be 400 years old. The tree has descending aerial roots that reach down to the ground from the lower branches, adding to the width of the trunk.

Dragon-trees have a red sap, known as 'dragon's blood', which has traditionally been used as medicine, a high-quality varnish for staining violins and for embalming the dead.

A trendy newcomer?

Dragon-trees may be labelled a "trendy newcomer" in Mike Wilcox's 2012 book, Auckland's Remarkable Urban Forest, but six of Auckland's dragon-trees were planted when Queen Victoria was on the throne.

They occur at three locations - in Remuera, Parnell and Devonport. All six of these old Auckland trees are remarkably different to those in the Canary Islands, and the more recent plantings around Auckland. Typically a densely branching tree, four of the old trees haven't branched at all and two have only sparingly branched.

Over-watering prevents flowering

Are these trees a different species, or a hybrid? An Ecology Professor from the Canary Islands, José María Fernández-Palacios, studied photographs of the odd Auckland trees. He explained that the lack of branching is because of an excess of water; such trees do not flower and therefore don't branch.

This form also occurred in the Canary Islands when they over irrigated the gardens or when they were planted beyond their distribution limits. The average rainfall of Tenerife is less than a quarter of the rainfall of Auckland.

Monitoring Auckland's dragon-trees

It is likely that all six of Auckland's historic dragon-trees were planted around the same time. The Parnell tree was planted in about 1898, making the six trees about 117 years old. It's difficult to explain why the modern plantings flower, fruit and branch so well when the older plants have not. Are they different genetic stock, or is it because nurseries haven't over-watered them? Time will tell.

Will Auckland's high rainfall affect the modern, well-branched, dragon-tree plantings such as this one in the centre of a roundabout in Newmarket. 9 Aug 2015.

Auckland War Memorial Museum - Tāmaki Paenga Hira.

Interestingly, although the dragon-tree is widespread throughout the world, wild dragon-trees are very rare in their native regions (apart from the remote Anti-Atlas Mountains). This slow-growing magnificent plant is unlikely to be a threat to the New Zealand environment, but the recent occurrence of wild seedlings from bird-transported seed in norther New Zealand makes it certainly worth keeping an eye on.